LEDs are capable of emitting high-brightness light with low electric power and are long in lifespan. Thus, the LEDs draw attention as light sources alternative to an incandescent lamp and a fluorescent lamp. The illuminance obtained by light emission of a single LED is lower than the illuminance of a HID lamp or the like. Thus, in an illumination device using an LED as a light source, a plurality of LEDs is used in order to realize a high illuminance. As one example of the illumination device of this kind, there is known an illumination device which includes a plurality of light sources disposed in a matrix form on one surface of a base having a rectangular flat plate shape (see, e.g., Japanese Unexamined Patent Application Publication No. 2009-129859)
The aforementioned illumination device capable of irradiating high-illuminance light is used for owl beam illumination that illuminates, for example, a ground or a stadium provided with night game equipment. In the owl beam illumination, it is necessary to determine light distribution so that light is not leaked to a residential area near a ground or the like.
For that reason, an optical member for controlling light distribution of the light emitted from LEDs needs to be used in an LED illumination device for owl beam illumination. Typically, in the owl beam illumination, the vertical light distribution is controlled at a predetermined angle. Thus, in an illumination device having a plurality of LEDs disposed in a matrix form, a plurality of elongated optical members for controlling light distribution of LEDs on a row-by-row basis is used in a parallel-arranged state.
However, even in the owl beam illumination, it is sometimes required to control not only the vertical light distribution but also the horizontal light distribution. In this case, it is necessary to individually provide optical members in individual LEDs instead of using an elongated optical member which collectively controls light distribution of a plurality of LEDs. However, it is typical that a larger number of LEDs are used in an LED illumination device of a higher luminance. In the case where the optical members are individually disposed in the LEDs and are fixed to the illumination device, the manufacturing process is time-consuming and the productivity is poor.